The present invention relates generally to cotton harvesters and, more specifically, to a drive arrangement for the row units on a cotton harvester including slip clutch structure for preventing row unit component failures.
A typical cotton harvester such as the John Deere Model 9950 Cotton Picker includes a plurality of transversely spaced row units with upright housings supporting harvesting structure which is driven by a transmission within the housing. The transmission, in turn, is driven by an output gear on a vertical shaft extending downwardly into the unit from a gear case located on top of the unit. In a four-row unit, two units are driven by a fore-and-aft extending drive shaft extending from the engine area on the harvester frame. A resetting slip clutch is provided at the input of the first unit, and the second unit is driven from the first unit with overload protection being provided by the single slip clutch. With such an arrangement, the release torque setting is sufficiently high to drive the two units but low enough to give adequate protection for each individual unit. A problem, when the units are cold and the picker bars are full of grease, is that the torque is equally divided between the two units and in the cold conditions may actually exceed the desired release torque setting on the single slip clutch and cause premature slipping of the slip clutch. When this happens, the operator, rather than waiting for the row unit to warm up and the torque to lower below the release torque of the slip clutch, will tighten the slip clutch so that the units will operate immediately in the cold conditions. Once the torque setting is increased and the units are warmed up, the normal running torque of a warmed up unit is sufficiently low that if one row unit on the drive arrangement plugs with cotton or another problem exists that causes an overload in the row unit, the increased torque limit can actually cause major damage to the row unit before the slip clutch starts slipping.
A second problem which exists with the presently available torque-limited drive systems occurs in combination with new narrow row cotton pickers which harvest five or six rows of cotton simultaneously. With five- or six-row harvesting, two or three units must be driven from a single main drive shaft. With three units on a drive arrangement, the problem of cold picker unit start-up is compounded and, in addition, the release torque setting must be increased thereby reducing the protection each individual unit receives from the slip clutch. Therefore, with the increased number of row units driven from a single torque-limited drive arrangement, there is more potential for unit component failures, especially in the picker bar area of the row unit.